Why is it hard to compute $$(g^x\ mod\ p, g^y\ mod\ p) \rightarrow g^{xy}\ mod\ p $$
How$$(g^x\bmod p, g^y\bmod p) \longmapsto g^{xy}\bmod p $$ when can we quickly compute $$x \rightarrow g^x\ mod\ p\\ y \rightarrow g^y\ mod\ p$$$$x \longmapsto g^x\bmod p$$ ?
